From 6827f0d7722ae08cf25cf2212f78bfc6ab8bfd0d Mon Sep 17 00:00:00 2001
From: Joel Sing <joel@sing.id.au>
Date: Tue, 14 Mar 2023 20:50:38 +1100
Subject: [PATCH] runtime: provide and use a GO_PPC64X_HAS_FUNCDESC define

Rather than implying that all ppc64 GOARCHs use function descriptors,
provide a define for platforms that make use of function descriptors.
Condition on GO_PPC64X_HAS_FUNCDESC when choosing whether or not
to load the entry address from the first slot of the function
descriptor.

Updates #56001.

Change-Id: I9cdc788f2de70a1262c17d8485b555383d1374b5
Reviewed-on: https://go-review.googlesource.com/c/go/+/476117
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
---
 src/runtime/asm_ppc64x.h     | 14 ++++++++++++++
 src/runtime/asm_ppc64x.s     | 14 ++++++--------
 src/runtime/cgo/asm_ppc64x.s |  6 ++----
 3 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/src/runtime/asm_ppc64x.h b/src/runtime/asm_ppc64x.h
index 5e55055fdbc..cce5537a9cb 100644
--- a/src/runtime/asm_ppc64x.h
+++ b/src/runtime/asm_ppc64x.h
@@ -23,3 +23,17 @@
 // and currently always use that much, PIC on ppc64 would need to use 48).
 
 #define FIXED_FRAME 32
+
+// aix/ppc64 uses XCOFF which has function descriptors.
+#ifdef GOOS_aix
+#ifdef GOARCH_ppc64
+#define GO_PPC64X_HAS_FUNCDESC
+#endif
+#endif
+
+// linux/ppc64 uses ELFv1 which has function descriptors.
+#ifdef GOOS_linux
+#ifdef GOARCH_ppc64
+#define GO_PPC64X_HAS_FUNCDESC
+#endif
+#endif
diff --git a/src/runtime/asm_ppc64x.s b/src/runtime/asm_ppc64x.s
index 37472c0f794..96a25f4047e 100644
--- a/src/runtime/asm_ppc64x.s
+++ b/src/runtime/asm_ppc64x.s
@@ -38,13 +38,13 @@ TEXT runtime·rt0_go(SB),NOSPLIT|TOPFRAME,$0
 	MOVD	R3, (g_stack+stack_lo)(g)
 	MOVD	R1, (g_stack+stack_hi)(g)
 
-	// if there is a _cgo_init, call it using the gcc ABI.
+	// If there is a _cgo_init, call it using the gcc ABI.
 	MOVD	_cgo_init(SB), R12
 	CMP	R0, R12
 	BEQ	nocgo
-#ifdef GOARCH_ppc64
-	// ppc64 use elf ABI v1. we must get the real entry address from
-	// first slot of the function descriptor before call.
+
+#ifdef GO_PPC64X_HAS_FUNCDESC
+	// Load the real entry address from the first slot of the function descriptor.
 	MOVD	8(R12), R2
 	MOVD	(R12), R12
 #endif
@@ -597,10 +597,8 @@ g0:
 	// This is a "global call", so put the global entry point in r12
 	MOVD	R3, R12
 
-#ifdef GOARCH_ppc64
-	// ppc64 use elf ABI v1. we must get the real entry address from
-	// first slot of the function descriptor before call.
-	// Same for AIX.
+#ifdef GO_PPC64X_HAS_FUNCDESC
+	// Load the real entry address from the first slot of the function descriptor.
 	MOVD	8(R12), R2
 	MOVD	(R12), R12
 #endif
diff --git a/src/runtime/cgo/asm_ppc64x.s b/src/runtime/cgo/asm_ppc64x.s
index c2010050444..fea749670b8 100644
--- a/src/runtime/cgo/asm_ppc64x.s
+++ b/src/runtime/cgo/asm_ppc64x.s
@@ -30,10 +30,8 @@ TEXT crosscall2(SB),NOSPLIT|NOFRAME,$0
 	BL	runtime·reginit(SB)
 	BL	runtime·load_g(SB)
 
-#ifdef GOARCH_ppc64
-	// ppc64 use elf ABI v1. we must get the real entry address from
-	// first slot of the function descriptor before call.
-	// Same for AIX.
+#ifdef GO_PPC64X_HAS_FUNCDESC
+	// Load the real entry address from the first slot of the function descriptor.
 	MOVD	8(R3), R2
 	MOVD	(R3), R3
 #endif